State 1
Reference

The Reference State (State 1) for the Shallow Loamy Ecological Site is dominated by mid-stature, cool-season bunchgrasses and rhizomatous wheatgrasses. This state persisted under grazing by large ungulates and was a resource for forage and habitat for a variety of wildlife.

The Reference State (State 1) has been determined by study of rangeland relic areas, or areas protected from excessive disturbance. Trends in plant communities going from heavily grazed areas to lightly grazed areas, seasonal use pastures, and historical accounts have also been used.

Characteristics and indicators. The Reference State (State 1) is characterized by the prominent cover of bluebunch wheatgrass (25-50 percent composition) and rhizomatous wheatgrasses (25-50 percent composition) such as Montana wheatgrass and western wheatgrass. Indian ricegrass and needle and thread also make up a significant portion of foliar cover (5-15 percent composition). Shrubs such as Wyoming big sagebrush and yellow rabbitbrush are primarily a minor component (5-20 percent composition) but will increase as the plant community moves away from Reference State conditions.

Resilience management. The state is stable and well adapted to the Central Rocky Mountains climate. The diversity in plant species provides resistance to influence from drought, non-native species, etc. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).

Community 1.1
Bluebunch Wheatgrass/Needle and Thread Wheatgrasses Plant Community

The interpretive plant community for this site is the Historic Climax Plant Community. This state evolved with grazing by large herbivores, soils less than 20 inches, and periodic fires. The cyclical nature of the fire regime in this community prevents big sagebrush from being the dominant species. This plant community can be found on areas that are properly managed with grazing and/or prescribed burning, and on areas receiving occasional short periods of rest. Potential vegetation is about 75% grasses or grass-like plants, 10% forbs, and 15% woody plants. Cool season midgrasses dominate the state.

The major grasses include bluebunch wheatgrass, needleandthread, Indian ricegrass, and
rhizomatous wheatgrass. Other grasses occurring on the state include Sandberg bluegrass, prairie junegrass, and bottlebrush squirreltail. Green needlegrass and spikefescue occur in the upper limit of this precipitation zone. Black and big sagebrush are conspicuous elements of this state, which can make up 10% of the annual production. A variety of forbs also occurs in this state and plant diversity is high (see Plant Composition Table).

The total annual production (air-dry weight) of this state is about 500 pounds per acre, but it can range from about 350 lbs./acre in unfavorable years to about 700 lbs./acre in above average years.

Resilience management. The state is extremely stable and well adapted to the Northern Intermountain Desertic Basins climate. The diversity in plant species allows for high drought resistance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).

Community 1.2
Perennial Grass/Mixed Shrub Plant Community

Historically, the Perennial Grass/Mixed Shrub Plant Community evolved under grazing and a low fire frequency. Currently, it is found under moderate, season-long grazing by livestock and will be exacerbated by prolonged drought conditions. In addition, the fire regime for this site has been modified and extended periods without fire are now common. This plant community is still dominated by cool-season grasses, while short warm-season grasses and miscellaneous forbs account for the balance of the understory. A variety of shrubs is now a conspicuous part of the overall production.

The dominant grasses include bluebunch and Montana wheatgrasses, rhizomatous wheatgrasses, and needle and thread. Grasses and grass-like species of secondary importance include prairie Junegrass, blue grama, Sandberg bluegrass, and threadleaf sedge. Green needlegrass and spike fescue occur on sites in the upper limit of this precipitation zone. Forbs commonly found in this plant community include scarlet globemallow, prairie sagewort, fleabanes, leafy wildparsley, and phlox. Wyoming big sagebrush, black sagebrush, yellow rabbitbrush and winterfat dominate the overstory. Shrubs can make up to 20% of the annual production. The overstory of shrubs and understory of grass and forbs provide a diverse plant community.

When compared to the Reference Plant Community (1.1), shrubs, prairie Junegrass, and blue grama have increased. Plains pricklypear cactus may also have invaded, but occurs only in small patches. Indian ricegrass and bluebunch and/or Montana wheatgrasses has decreased and Indian ricegrass may occur in only trace amounts under the sagebrush canopy or within the patches of pricklypear. In addition, the amount of winterfat may or may not have changed depending on the season of use.

The total annual production (air-dry weight) of this state is about 425 pounds per acre, but it can range from about 250 lbs./acre in unfavorable years to about 650 lbs./acre in above average years.

Resilience management. This plant community is resistant to change. The herbaceous species present are well adapted to grazing; however, species composition can be altered through long-term overgrazing. The herbaceous component is mostly intact and plant vigor and replacement capabilities are sufficient. Water flow patterns and litter movement may be occurring but only on steeper slopes. Incidence of pedestalling is minimal. Soils are mostly stable and the surface shows minimum soil loss. The watershed is functioning and the biotic community is intact.

Pathway 1.1A
Community 1.1 to 1.2

Moderate, Continuous Season-long Grazing and/or Drought Moderate, continuous season-long grazing will convert the plant community to the Perennial Grass/Mixed Shrub Plant Community (1.2). Prolonged drought will exacerbate this transition.

Pathway 1.2A
Community 1.2 to 1.1

Prescribed Grazing, Long-term Prescribed Grazing, or Wildfire Prescribed grazing or possibly long-term prescribed grazing, will convert this plant community to the Reference Plant Community (1.1). The probability of this occurring is high especially if rotational grazing along with short deferred grazing is implemented as part the prescribed method of use. In addition, the removal of fire suppression will allow a somewhat natural fire regime to reoccur to more easily transition between this plant community and the Reference Plant Community (1.1). A prescribed fire treatment can be useful to hasten this transition if desired.

State 2
Mixed Shrub and Bare Ground

The Mixed Shrub and Bare Ground state of the Shallow Loamy Ecological Site is dominated by shrubs as a result of extensive grazing and lack of fire. Preferred cool season grasses have been highly reduced. Remnant grasses missed by grazers such as prairie Junegrass, Sandberg bluegrass, and blue grama dominate the grass/grasslike composition. Bare ground is prominent in the interspaces between plants in this state.

Characteristics and indicators. The Mixed Shrub/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> State is characterized by the prominent cover of Wyoming big sagebrush (>20 percent composition). Bare ground is prevalent in the interspaces between plants. Prairie Junegrass, Sandberg bluegrass, and blue grama continue to occur (10-40 percent composition).

Resilience management. The state is resistant to change and may become more fire resistant as fine fuels are reduced by continued frequent and severe grazing. Plant diversity is is moderate to poor making it more susceptible to the effects of drought or disease. Soil erosion is accelerated with the increase in bare ground and frequently result in water flow patterns on the surface.

Community 2.1
Mixed Shrub/Bare Ground Community

This plant community is the result of frequent and severe grazing and protection from fire. Soils on these sites are typically low in soluble salts. Shrubs and especially sagebrush dominate this plant community, as the annual production of sagebrush exceeds 20%. Shrubs are significant components of the plant community and the preferred cool season grasses have been eliminated or greatly reduced.

The dominant grasses/grasslikes are prairie Junegrass, Sandberg bluegrass, threadleaf sedge, and blue grama. Weedy annual species such as cheatgrass may occupy the site if a seed source is available. Plains pricklypear cactus often invades. Noxious weeds such as Russian knapweed, leafy spurge, or Canada thistle may invade the site if a seed source is available. The interspaces between plants have expanded leaving the amount of bare ground more prevalent. As compared with the Reference Plant community (1.1) or the Perennial Grass/Mixed Shrub Plant Community (1.2), the annual production is reduced, but the shrub production compensates for some of the decline in the herbaceous production.

The total annual production (air-dry weight) of this state is about 250 pounds per acre, but it can range from about 150 lbs./acre in unfavorable years to about 350 lbs./acre in above average years.

Resilience management. This plant community is resistant to change as the stand becomes more decadent. These areas may actually be more resistant to fire as less fine fuels are available and the bare ground between the sagebrush plants is increased. Continued frequent and severe grazing or the removal of grazing does not seem to affect the composition or structure of the plant community. Plant diversity is moderate to poor. Soil erosion is accelerated because of increased bare ground. Water flow patterns and pedestalling are obvious. Infiltration is reduced and runoff is increased. Rill channels may be noticeable in the interspaces and gullies may be establishing where rills have concentrated down slope.

State 3
Sod Bound

The Sod-Former State of the Shallow Loamy Ecological Site is dominated by sod-forming grasses and grasslikes. This state occurs as a result of frequent and severe grazing and removal of brush either naturally (drought, fire) or human brush control methods. preferred cool-season grasses and shrubs are greatly reduced or lacking completely.

Characteristics and indicators. The Sod-Former State of the Shallow Loamy Ecological Site is characterized by the prominent cover of blue grama and threadleaf sedge in large patches (25-70 percent cover). Overall production is greatly reduced compared the Reference State and Mixed Shrub/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> State.

Resilience management. The Sod-Former state is extremely resistant to change and the plant diversity is extremely low. Water infiltration is greatly reduced which protects that site itself but can result in increased runoff around the edges of the mat.

Community 3.1
Blue Grama Sod Plant Community

This plant community is the result of frequent and severe yearlong grazing, which has adversely affected the perennial grasses as well as the shrub component. Other factors that can affect the shrubs include drought, heavy browsing, wildfires, and/or human brush control measures. A dense sod of blue grama with patches of threadleaf sedge dominates this site. Plains pricklypear cactus can become dense enough in patches so that livestock cannot graze forage growing within the cactus clumps. Sagebrush has been significantly reduced and in some cases removed.

When compared to the Reference State (State 1), blue grama and threadleaf sedge have increased. Weedy annual species may also dominate and exist in large patches. These include cheatgrass, Russian thistle, and annual mustards. All cool-season mid-grasses and forbs have been greatly reduced and the shrub component is lacking. Total production has been significantly decreased.

The total annual production (air-dry weight) of this state is about 150 pounds per acre, but it can range from about 100 lbs./acre in unfavorable years to about 250 lbs./acre in above average years.

Resilience management. This sod is extremely resistant to change and continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the plant community. The biotic integrity of this state is not functional and plant diversity is extremely low. This sod bound plant community is very resistant to water infiltration. While this sod protects the site itself, areas amid these patches or off-site areas are affected by excessive runoff that can cause rills and gully erosion. Water flow patterns are obvious in the bare ground areas and pedestalling is apparent along the sod edges. Rill channels are noticeable in the interspaces and down slope. The watershed may or may not be functioning, as runoff may affect adjoining sites.

State 4
Invaded

Wyoming rangelands, much like the neighboring states, has quickly fallen victim to the aggressive invasion of cheatgrass, also called downy brome (Bromus tectorum). The rapid development of an extensive seedbank and duff layer forms with the potential for multiple growth cycles throughout a year. The advantageous ability of cheatgrass to persist through the winter under a blanket of snow and sprout early makes it difficult for natives to outcompete it for limited resources. Shifts in climatic patterns, changes in management, and exposure to human activity are a few of the explanations for the current flush and rapid expansion across the western United States. Although cheatgrass is the most prevalent large-scale threat for rangeland managers, a variety of knapweeds (spotted, Russian, etc.), in combination with other aggressive invaders such as whitetop (hoary cress), black henbane, field bindweed, and leafy spurge are increasing in density and frequency, producing their own set of challenging management issues. As more species are found or as other species become more prevalent on a large scale, the community dynamics in this state will shift in response to the concerns of the identified species.

Characteristics and indicators. The Invaded State (State 4) is characterized by the presence and eventual dominance of invasive and non-native species. The open canopy of the arid native community combined with extended periods of drought alone or in combination with overutilization, insect damage, or wildfire, has weakened the native composition, thus allowing invasion.

Resilience management. The competitive nature of annuals and other invasive species creates a complex environment that inhibits control and makes it implausible to attain complete eradication once an invasive species has established on the landscape.

Community 4.1
Invasive Plant Community

Downy brome, better known as cheatgrass (Bromus tectorum), can green-up and grow late into the fall and green-up early spring before snowmelt; this growth pattern allows cheatgrass to utilize fall and spring resources that are otherwise stored for the cool-season native vegetation before they can begin to break dormancy. The morphology of the seed allows for easy dispersal and longevity, creating a widespread and long-term seed bank. Seeds can persist for long periods of time until growing conditions are optimal, allowing growth before most native species. The ability of the plant to grow quickly, utilizing available resources and producing large quantities of seed rapidly, and to reproduce in poor conditions are what drive cheatgrass above the natives and many improved varieties of grass; as well as creates a management challenge that has not been successfully met at this time.

Once this species has a niche on a landscape it is resistant and resilient to change. The absence of sagebrush in this community restricts the potential for native herbaceous species, but some will persist in small scattered populations or sparsely under the canopy of cheatgrass. When climatic conditions are optimal, these resilient native species will respond to the available resources (typically mid-spring moisture). They are not able to out-compete invasive species long-term, so are restricted to a minor composition in the community. The ability for cheatgrass to emerge, bolt, produce seed, and mature two to three times within a year utilizes all available soil nutrients and moisture resources.

Chemical control is difficult to attain and maintain success without lasting effects on the native grasses in the area. Chlorosis of wheatgrasses, stunted plants, and loss of certain forbs are a few of the residual chemical effects: plateauing is what has been observed in this region. This generally comes from the chemical composition and its ability to bind to the chemistry or nutrients in the soil, inhibiting the uptake by roots.

The risk, frequency and intensity of wildfires increase with the increasing fine fuels (biomass load) created by cheatgrass. The fire frequency interval has been noted to shift to a possible five-year cycle, preventing sagebrush and other woody species from establishing on the site. Negative impacts on many of the native herbaceous species in the understory are intensified by increased evaporation and mineralization or vaporization of many of the nutrients, rendering the soils nearly sterile. The grazing potential is limited due to the unpalatable and harsh environment that the mature seeds create with their long awns and chaff. If grazed in early spring or late fall some of this can be avoided, but general use through the middle of the growing season is difficult and defeats the purpose of intensively grazing the location. In smaller invaded sites or under certain conditions, grazing can be used as a tool within the integrated pest management toolbox, but it is not effective alone.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change. Plant diversity is poor. The plant vigor is diminished, and replacement capabilities are non-existent due to the loss of cool-season grasses. Plant litter is noticeably more when compared to Reference State plant communities in response to the dense duff layer created by cheatgrass. Soil erosion generally is reduced in response to the litter accumulation. Infiltration and runoff are variable due to the loss of perennial vegetation, but with the potential increase in root density. Overall biotic integrity is lost in this community.

Transition T1A
State 1 to 2

Frequent and Severe Grazing and No Fire Frequent and severe grazing plus no fire will convert the plant community to the Mixed Shrub/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> Plant Community. The probability of this occurring is high, especially evident on areas with historically higher precipitation and where drought or heavy browsing does not adversely impact the sagebrush stand.

Transition T1B
State 1 to 3

Frequent and Severe Grazing (Yearlong) and Wildfire or Brush Management w/Drought Frequent and severe grazing (yearlong grazing) plus wildfire or brush control, will convert the plant community to the Sod-Former State. The probability of this occurring is high, especially if the sagebrush stand has been severely affected by drought or heavy use or has been removed altogether.

Constraints to recovery.The ability to weaken or break up the sod-forming species and the lack of remaining native (key) bunchgrasses are the main constraints to recovery for this community.

Context dependence.The time lapse for the occurrence of this state is varied. It is a transition that takes or may take a significant time frame (over ten years) to occur. Recovery may be able to be achieved; but at this time no proof of recovery, without mechanical interference, has been achieved/documented within a management time frame (25 years).

Restoration pathway R2A
State 2 to 1

Brush Management, Prescribed Grazing, and Seeding Brush management, followed by prescribed grazing, will return this plant community at or near the Reference State (State 1). Reseeding after brush management with native species may be necessary to ensure a more rapid transition. If prescribed fire is used as a means to reduce or remove the shrubs, sufficient fine fuels will need to be present. This may require deferment from grazing prior to treatment. Post management is critical to ensure success. This can range from two or more years of rest to partial growing season deferment, depending on the condition of the understory at the time of treatment and the growing conditions following treatment. In the case of an intense wildfire that occurs when desirable plants are not completely dormant, the length of time required to reach the Reference State (State 1) may be increased and seeding of natives is recommended.

Transition T2A
State 2 to 3

Brush Management and Frequent and Severe Grazing Brush management, or an intense wildfire followed by frequent and severe grazing, will convert the plant community to the Sod-Former State.

Transition T2B
State 2 to 4

Wildfire, Frequent or Severe Grazing, Drought with Insect Damage/Brush Management Fire (wild), Frequent or Severe Grazing, Drought with Insect Damage/Brush Management – Throughout most of this LRU there is a seed source present for cheatgrass, knapweed, and other invasive species. Stress to the native community from fire, drought, disease/insect damage to sagebrush, or ground/soil disturbance including impacts by grazing large herbivores or recreational uses; opens the canopy and exposes the soil, creating a niche for undesirable and invasive species to establish. Early detection and rapid response provides a chance to prevent a full-scale invasion, but if left untreated, infestations can establish rapidly and spread with one growing season. The population soon grows exponentially as further stress or disturbance occurs. In some cases, once the invasive species are established, they can create their own habitat; this reduces the competitive ability of native species. The open canopy of the Mixed Shrub/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> State is vulnerable to invasive species without further influence. With continued over-use, drought, or insect damage/disease, the invasive species will establish and quickly dominate a location. The threshold species in this system is Wyoming big sagebrush, which protects the remnants of the perennial native grasses, allowing them to persist on the landscape.

Constraints to recovery.The lack of sufficient key native species and the inability to eradicate or sufficiently control invasive species are the main constraints to recovery for this state.

Context dependence.Extent of the transition for the Mixed Shrub/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> State to the Invaded State will determine the severity of the recovery constraints. The loss of shrubs from this state will further limit/remove any ability of this state to recover back to any previous state.

Restoration pathway R3A
State 3 to 1

Grazing Land Mechanical Treatment, Prescribed grazing and Seeding Grazing land mechanical treatment (chiseling, etc.) and plains pricklypear cactus control (if needed), followed by prescribed grazing, will return this plant community to near Reference State (State 1) condition. Reseeding with natives is often needed to hasten this transition.

Transition T3A
State 3 to 4

Frequent and Severe Grazing, Drought, Disturbance, and Non-native seed source present Frequent and severe grazing, drought, or disturbance with a seed source present—Increased interspatial gaps in these communities leaves exposed soil that is vulnerable to invasion by undesirable species. Increased pressure from overuse and drought work to weaken the sod or mat-like community, exposing soil further to annuals and other invaders, such as cheatgrass and knapweeds. The aggressive nature and altered hydrology of these sites do restrict weed invasion. But if a seed source is available, ground disturbance by herbivores or man-induced, allows invasive species to find a way into the community. Once established in the community, it may not be feasible to completely remove eradicate the invasive species. Once the invasive species have become prevalent on the landscape (less than 5 percent composition), the community crosses the threshold into the Invaded State.

Constraints to recovery.The lack of ability to eradicate or remove invasive species from the community at this time is the constraint to any recover from the invader driven state.

Context dependence.Substantial evidence that a blue grama dominated community has shifted to a invaded community has not been gathered. It has been documented where a significant population of invasive species (ex: cheatgrass) has established within the interspaces of the blue grama sod.